Thanks for the answers. What I meant was if it was possible to detect directly on the control channel (of a MotoTRBO Connect+ system) if a talkgroup is encrypted.
No, only way of knowing on DMR is to get the PI header or the SVC enc bit set during full link control for the voice call (after you've tuned to it). Its not broadcast over the air on the CC or anything like a PDU. Not sure, but I suppose some software could lock these out if desired in order to limit repeat tuning to the same enc voices by internalizing which groups it has observed to be enc or similar. Unless its available in some form of Proprietary PDU data.
On P25, the only thing I'm aware of is the MFID A4 Group Regroup Explicit Encryption Command PDU. This is supposed to broadcasts which groups/supergroups are enc and which alg/key they use, but my observation is that its more of a suggestion than set in stone, as listeners on the site I've seen the PDU on (Duke Energy P25) say they've heard the groups in the PDU in the clear, regardless of what the PDU suggests.
Code:
12:41:40 P25p2 VCH 1 MAC_SIGNAL
MFIDA4 Group Regroup Explicit Encryption Command
SG [64605] KEY [0001] ALG [84]
WGID [60100][EAC4] WGID [60101][EAC5]
P25 PDU Payload
[1C][B0][A4][0D][67][FC][5D][00][01][84][EA][C4]
[EA][C5][08][05][88][88][88][01][AB][DE][80][00]